By adding a hand pulling, the short distance knee kick and face punch can work well.
Getting back to the OP's question regarding simultaneous double strikes, Yes, in Wing Chun simultaneous double strikes, and even
triple strikes, are often demonstrated as illustrations of the style's well known emphasis on efficiency. So, the theory goes, two or even three strikes landing at the same time gives you more bang for the buck, right?
...er
No. I'm with Tony on this one. When working against a resisting opponent we all quickly learn that it is hard enough to land a single solid hit at a time, regardless of style, and as Tony stated before, when you do land a hit, it is easier to focus your force into a single strike than to split it between two or more strikes.
So, in the beautifully posed demo picture above, we see a punch and kick hitting at the same moment and it seems very efficient. And indeed there is a very similar movement is found in the Dummy Form. Nevertheless, in reality, rather than a punch, a double
lap-sau (grappling-hand) and kick would be a higher percentage move than this simultaneous l
ap-da (punch-hit) and front kick. IMO this stuff is just for coordination training and for show.
Here's a photo of the late GM Yip Man posing a technique that makes more sense to me ande similar to the one I referred to above:
Com-na jeet gherk (a double
lap or grapple and shin kick).
https://i.pinimg.com/originals/dc/ea/0e/dcea0e81b38fdd5335a96ff8c3ee79d9.jpg
Interestingly, there
are a few double punch or double palm movements that are quite powerful and useful in very specific situations, especially some self defense scenarios, but I would say they are the "exceptions that prove the rule".